Radio base station device and radio communication method

ABSTRACT

A base transceiver station includes a baseband signal processor outputting a frequency notification signal indicating a carrier frequency for modulating a baseband signal, in combination with a baseband signal and a radio transmitter and receiver modulating the baseband signal from the baseband signal processor with the carrier frequency designated by the frequency notification signal so as to produce a radio transmission signal. By allowing the baseband signal processor to output the baseband signal and the frequency notification signal to the radio transmitter and receiver, the radio transmitter and receiver is immediately informed of the carrier frequency for modulation of the arriving baseband signal so that the radio transmitter and receiver is capable of generating a radio transmission signal efficiently and properly.

TECHNICAL FIELD

The present invention relates to a base transceiver station and a radiocommunication method of a multi-carrier type in which a baseband signalis modulated with a carrier frequency for radio transmission.

BACKGROUND ART

FIG. 2 shows an example of a base transceiver station of a code divisionmultiple access (CDMA) type. The base transceiver station comprisesantennas 21 and 22, a radio transmitter and receiver (TRX) 24, abaseband signal processor (BB) 25 and a call processing controller 26.

In this base transceiver station, a signal is received via the antennas21 and 22. The received signal is converted into a baseband signal bythe radio transmitter and receiver 24. The baseband signal processor 25subjects the baseband signal to spectrum despreading, error correctionand the like before transmitting it to a wire network. A signal receivedfrom the wire network is subject to spectrum spreading by the basebandsignal processor 25. The radio transmitter and receiver 24 produces aradio transmission signal by modulating the spread signal with a carrierof a predetermined frequency and transmits the modulated signal via theantennas 21 and 22.

In such a base transceiver station of a CDMA system, complex processesincluding multiplexing of multiple-channel signals and multiplexing of avariety of signals including a voice signal and a data signal arenecessary. Particularly, in a multi-carrier system, it is required thatthe radio transmitter and receiver 24 perform complex processesincluding using different carrier frequencies for different basebandsignals.

In the related art, the call processing controller 26 is configured tonotify the radio transmitter and receiver 24 of the carrier frequency tobe used for each of the different baseband signals so that the radiotransmitter and receiver 24 modulates the baseband signal with thedesired frequency in accordance with the notification. Thus, it isensured that different carrier frequencies are used for differentbaseband signals.

The frequency notification procedure as described above requires complexprocesses in that it is necessary for the call processing controller 26to notify the radio transmitter and receiver 24 of the carrier frequencyto be used for the baseband signal arriving at the radio transmitter andreceiver 24 in advance of modulation, and for the radio transmitter andreceiver 24 to modulate the arriving baseband signal with a propercarrier frequency.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a base transceiverstation and a radio communication method capable of efficiently andproperly modulating a baseband signal with a desired carrier frequencyin a simple process.

The present invention provides a base transceiver station comprising:

-   -   a baseband signal processor outputting a baseband signal and a        frequency notification signal indicating a carrier frequency for        modulation of the baseband signal; and    -   a radio transmitter and receiver modulating the baseband signal        from the baseband signal processor with the carrier frequency        indicated by the frequency notification signal so as to generate        a radio transmission signal.

Accordingly, the baseband signal processor outputs the frequencynotification signal as well as the baseband signal to the radiotransmitter and receiver so that the radio transmitter and receiver iscapable of instantaneously identifying the carrier frequency to be usedfor modulation of the arriving baseband signal so that the radiotransmission signal is produced efficiently and properly.

The baseband signal processor may output the frequency notificationsignal to the radio transmitter and receiver via a signal line fortransmission of a synchronization signal.

Accordingly, since the frequency notification signal is output via thesignal line for transmission of the synchronization signal, it is notnecessary to provide a separate signal line for frequency notificationso that the construction of the station is simplified.

The baseband signal processor may output a parity signal to the radiotransmitter and receiver via the signal line for transmission of thesynchronization signal.

Accordingly, the parity signal is output via the signal line fortransmission of the synchronization signal in addition to the frequencynotification signal so that it is not necessary to provide a separatesignal line for the parity signal and the construction of the station issimplified.

The present invention provides a radio communication method comprisingthe steps of:

-   -   assigning one of a plurality of carrier frequencies to a        baseband signal, based on a result of call process;    -   transmitting a baseband signal and a frequency notification        signal indicating the carrier frequency assigned to the baseband        signal, to a radio transmitter and receiver;    -   generating a radio transmission signal by modulating in the        radio transmitter and receiver the baseband signal with the        carrier frequency indicated by the frequency notification        signal; and    -   generating the radio transmission signal thus generated.

Accordingly, the radio transmission signal is generated efficiently andproperly by outputting the baseband signal and the frequencynotification signal. Since the carrier frequency is assigned to thebaseband signal based on the information obtained in the call process,it is ensured that the carrier frequency is assigned properly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an electrical construction of a radiocommunication system according to an embodiment of the presentinvention;

FIG. 2 is a block diagram showing an electrical construction of a basetransceiver station of FIG. 1;

FIG. 3 shows a construction of a base transceiver station of FIG. 2;

FIG. 4 shows transmission of a downstream signal from a baseband signalprocessor of FIG. 2 to a radio transmitter and receiver; and

FIG. 5 shows a data format occurring at {circle around (1)} and {circlearound (3)} of FIG. 4.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, various embodiments of the present invention will bedescribed with reference to the drawings.

FIG. 1 is a block diagram showing an electrical construction of a radiocommunication system according to an embodiment of the presentinvention. A radio network controller (RNC) 11 is connected to aplurality of base transceiver stations (BTS) 12 so as to control thebase transceiver stations 12. The base transceiver station 12communicates with a mobile station 13 using a radio signal andcommunicates with the radio network controller 11 over a wiretransmission channel.

With this construction, a signal from the mobile station 13 ismultiplexed by the base transceiver station 12 accommodating the mobilestation 13. Signals from a plurality of base transceiver stations 12 arein turn multiplexed by the radio network controller 11 so that thesignal from the mobile station 13 is transmitted to another radioterminal or a stationary terminal. It is thus ensured that voicecommunication or data transmission between a plurality of terminals isenabled.

FIG. 2 is a block diagram showing an electrical construction of the basetransceiver station 12 of FIG. 1. The base transceiver station 12 isprovided with an antenna (ANT1) 21, an antenna (ATN2) 22, an amplifier23, a plurality of radio transmitter and receivers (TRX) 24, a pluralityof baseband signal processors (BB) 25, and a control unit 36 including acall processing controller 26, a maintenance and monitoring controller27 and a wire transmission channel interface 28.

The antennas 21 and 22 constitute a pair for transmission diversity andreception diversity. The amplifier 23 amplifies a transmission signalfrom the radio transmitter and receiver 24 to a predetermined levelbefore delivering the amplified signal to the antennas 21 and 22. Theamplifier 23 also amplifies a signal received via the antennas 21 and 22to a predetermined level before delivering the amplified signal to theradio transmitter and receiver 24. The radio transmitter and receiver 24modulates the signal from the baseband signal processor 25 with one of aplurality of (for example, four) carrier frequencies before outputtingthe modulated signal to the amplifier 23. The radio transmitter andreceiver 24 also subjects the signal received via the antennas 21 and22, and via a low noise amplifier 29 to synchronous detection beforeoutputting it to the baseband signal processor 25.

The baseband signal processor 25 is provided with various functions forbaseband processes. More specifically, the baseband signal processor 25subjects transmission data to error correction encoding, frameconstruction, data modulation, spectrum spreading and the like. Areceived signal undergoes spectrum despreading, chip synchronization,error correction decoding, data separation and maximal ratio combiningperformed in concurrence with diversity handover.

The call processing controller 26 has a call process application builttherein and communicates with the radio network controller 11 using acall processing control signal so as to manage, set and release radiotransmission channels, monitor a call process and control calls. Themaintenance and monitoring controller 27 has a maintenance andmonitoring control application built therein and communicates with theradio network controller 11 using a maintenance and monitoring controlsignal so as to manage the status of the base transceiver station 12,manage the history of status change of the base transceiver station 12,control the status of the base transceiver station 12 and perform remotefile transmission. The wire transmission channel interface 28 isprovided with a wire transmission channel terminating function.

A description will now be given of upstream signal transmission in theconstruction described above. The radio signal from the radio terminalis received by the antennas 21 and 22 of the base transceiver station12, amplified by the low noise amplifier 29 and processed by the radiotransmitter and receiver 24. More specifically, each of an I-componentand a Q-component of the received radio signal is subject to synchronousdetection so as to produce an I baseband signal and a Q baseband signalorthogonal to each other. The isolated baseband signals are then subjectto spectrum despreading by the baseband signal processor 25. The signalrecovered by the despreading is transmitted to the radio networkcontroller 11 via the wire transmission channel interface 28.

A description will now be given of a downstream signal. The signal fromthe radio network controller 11 is separated into the I-component andthe Q-component for spreading modulation by the baseband signalprocessor 25 before being transmitted to the radio transmitter andreceiver 24. In this process, the call processing controller 26 notifiesthe baseband signal processing unit 25 of the carrier frequency formodulating the signal stream being processed, based on informationobtained in the call process. The baseband signal processor 25 transmitsa frequency notification signal indicating the designated carrierfrequency to the radio transmitter and receiver 24 in combination withthe signal stream being processed. The signal stream (I, Q) from thebaseband signal processor 25 is subject to quadrature modulation by theradio transmitter and receiver 24 using the carrier having the frequencyindicated by the frequency notification signal. The modulated signal isamplified by the amplifier 23 before being transmitted via the antennas21 and 22.

A brief description will be given of the call process. When the mobilestation 13 accesses the circuit, the mobile station 13 selects from aplurality of carrier frequencies arriving from the base transceiverstation 12 the frequency characterized by the largest received powerintensity. The call processing controller 26 of the base transceiverstation 12 secures a radio circuit of the carrier frequency selected bythe mobile station 13 and also provides radio circuit informationindicating the secured circuit to the baseband signal processor 25. Thecarrier frequency information contained in the radio circuit informationthus provided is coupled with the respective baseband signal and outputto the radio transmitter and receiver 24.

Thus, since the baseband signal processor 25 outputs not only thebaseband signal but also the carrier frequency information to the radiotransmitter and receiver 24, the radio transmitter and receiver 24 iscapable of instantaneously identifying the carrier frequency with whichto modulate the arriving baseband signal so as to produce the radiotransmission signal efficiently and properly. By configuring the callprocessing controller 26 to assign the carrier frequency to the basebandsignal based on the information obtained in the call process, it isensured that the carrier frequency is assigned properly.

FIG. 3 shows a physical construction of a base transceiver station ofFIG. 2. The radio transceiver (TRX) 24, the baseband signal processor(BB) 25, the call processing controller 26, the maintenance andmonitoring controller 27 and the wire transmission channel interface 28are implemented by respective printed circuit boards of a cardconfiguration. The housing of the base transceiver station is providedwith shells for accommodating the cards. The back plane of the basetransceiver station is provided with a backwired board (BWB) 31 formutual connection between the cards.

The radio transmitter and receiver 24 accommodated in the upper shell isresponsible for modulation at one of carrier frequencies fA and fB. Theradio transmitter and receiver 24 accommodated in the lower shell isresponsible for modulation at one of the carrier frequencies fC and fD.All the baseband signal processor 25 accommodated in the upper and lowershells are adapted for any of the four (A–D) carrier frequencies.Instructions from the call processing controller 26 enable dynamicassignment of the carrier frequency to the baseband signal processor 25.

FIG. 4 shows downstream signal transmission from the baseband signalprocessor to the radio transmitter and receiver of FIG. 2. The backwiredboard 31 disposed between the baseband signal processor 25 and the radiotransmission and receiver 24 is a printed circuit board connecting eachof the baseband signal processors 25 with a corresponding one of theradio transmitter and receiver 24. Each of the baseband signalprocessors 25 is provided with a modulator (MOD) 32 and a serializer(SER) 33. The radio transmitter and receiver 24 is provided with amultiplexer 35 and a set of deserializers (DES) 34 each corresponding tothe respective one of the baseband signal processors 25.

The signal subjected to spreading modulation by the modulating unit 32is transmitted to the serializer 33 with a 9-bit width. The serializer33 converts the modulated signal into a 1-bit width (differential pair)serial data, which is then transferred to the deserializer 34 of theradio transmitter and receiver 24 via the backwired board 31. Thedeserializer 34 returns the serial data into a 9-bit width signal. Themultiplexer 35 multiplexes the signals from the baseband signalprocessors 25.

By allowing the serializer 33 to convert the downstream signal from thebaseband signal processor 25 to the radio transmitter and receiver 24into a signal having a smaller bit width for high-speed transmission inthe backwired board 31, the required width of transmission channel isreduced so that the limited area for wiring is effectively utilized.

FIG. 5 shows a data format occurring at {circle around (1)} and {circlearound (3)} of FIG. 4. A first bus line 41 and a second bus line 42 aresignal lines for transmitting an I-component via the antenna 21. Thefirst bus line 41 is responsible for a first set of 8 bits and thesecond bus line 42 is responsible for a second set of 8 bits, the firstset and the second set being transmitted alternately over the air.Similarly, a third bus line 43 and a fourth bus line 44 transmit aQ-component signal transmitted via the antenna 21, a fifth bus line 45and a sixth bus line 46 transmit an I-component signal transmitted viathe antenna 22. A seventh bus line 47 and an eighth bus line 48 transmita Q-component signal transmitted via the antenna 22.

A ninth bus line 49 is a signal line for transmission of asynchronization signal. A parity bit (P) is placed at the head, followedby two bits (F0, F1) for carrier frequency notification. The last 5 bitsare used as a synchronization flag.

By outputting the frequency notification signal via the ninth bus line49, there is no need to provide a separate signal line for frequencynotification. Accordingly, the construction of the station issimplified. The parity signal is also output via the ninth bus line 49for transmission of a synchronization signal. Accordingly, there is noneed to provide a separate parity signal line so that the constructionof the station is further simplified.

INDUSTRIAL APPLICABILITY

The base transceiver station and radio communication method according tothe present invention is applicable to a radio communication system of,for example, a CDMA system.

1. A base transceiver station comprising: a baseband signal processorconfigured to output a baseband signal and a frequency notificationsignal indicating a carrier frequency for modulation of the basebandsignal, the indicated carrier frequency being obtained based on acarrier frequency having a largest received power intensity at a mobilestation during a call process; and a radio transmitter and receiverconfigured to modulate the baseband signal from said baseband signalprocessor with the carrier frequency indicated by the frequencynotification signal so as to generate a radio transmission signal. 2.The base transceiver station according to claim 1, wherein said basebandsignal processor outputs the frequency notification signal to said radiotransmitter and receiver via a signal line for transmission of asynchronization signal.
 3. The base transceiver station according toclaim 2, wherein said baseband signal processor outputs a parity signalto said radio transmitter and receiver via the signal line fortransmission of the synchronization signal.
 4. A radio communicationmethod comprising assigning one of a plurality of carrier frequencies toa baseband signal, the carrier frequency being assigned based on acarrier frequency having a largest received power intensity at a mobilestation during a call process; transmitting a baseband signal and afrequency notification signal indicating the carrier frequency assignedto the baseband signal, to a radio transmitter and receiver; generatinga radio transmission signal by modulating in the radio transmitter andreceiver the baseband signal with the carrier frequency indicated by thefrequency notification signal; and transmitting the radio transmissionsignal thus generated.
 5. A base transceiver station comprising: abaseband signal processor configured to output a baseband signal and afrequency notification signal indicating a carrier frequency formodulation of the baseband signal; and a radio transmitter and receiverconfigured to modulate the baseband signal from said baseband signalprocessor with the carrier frequency indicated by the frequencynotification signal so as to generate a radio transmission signal,wherein said baseband signal processor outputs the frequencynotification signal to said radio transmitter and receiver via a signalline for transmission of a synchronization signal.
 6. The basetransceiver station according to claim 5, wherein said baseband signalprocessor outputs a parity signal to said radio transmitter and receivervia the signal line for transmission of the synchronization signal.